Rotor blades made of fiber-composite materials are used especially in rotors of modern rotary-wing aircraft such as, for example, helicopters, because of their special suitability for high, alternating dynamic and aerodynamic loads. In recent times, such rotor blades have been increasingly equipped with special functional devices that make it possible, for example, to systematically influence the aerodynamic and acoustic properties of a rotor. These functional devices can be, for example, actuators for an adjustable rotor blade flap arranged near the tip of the rotor blade, sensors installed on the rotor blade, a heating unit in the rotor blade, or the like. Especially well-suited actuators for adjustable rotor blade flaps are piezoelectric actuators that are actuated or controlled electrically. Power and signal transmission cables are required to supply power to such functional devices or else for signal or data transmission. Starting from an interface on the side of the rotor head or from a blade connection area of the rotor blade, these cables often have to extend over a large part of the span of the rotor blade all the way to the functional device (and sometimes back again as well).
During rotor operation, the rotor blades are subjected to extreme stresses and strains due to the enormous centrifugal forces of up to about 1000 grams or more. Moreover, the rotor blades are severely deformed by alternating dynamic and aerodynamic forces during a rotation of the rotor blade. During a rotation of the rotor blade, the rotor blades execute flapping, tilting and twisting movements that lead to a bending and twisting of the fiber-composite rotor blade structure. If the rotor blade is equipped with power and signal transmission cables, it has been found that, under the described high dynamic loads, the wires or conductors of the cable very quickly break or fail. Especially electric signal or power transmission cables having metal wires or conductors fail quite soon. Consequently, sufficient fatigue strength of the cable can no longer be ensured. The result of this, in turn, is that it is not possible to ensure reliable operation of the appertaining functional device that is being supplied with power by such a cable or that receives or emits signals via such a cable. Moreover, if the cable fails, the appertaining rotor blade in which this cable is installed has to be replaced or repaired. This, however, entails tremendous technical effort and costs.
In the case of certain applications or cable designs, for example, coaxial cables or the like, it is also necessary for the wires/conductors of the cable to be shielded. However, it has been found that the shielding of these cables also fails too soon as a result of the above-mentioned high centrifugal forces so that reliable shielding cannot be ensured.
The installation of power and/or signal transmission cables in the rotor blade is also very complex. Up until now, conventional cables of the above-mentioned type have been laid in cable conduits that are created on the surface in the fiber-composite rotor blade structure and in the predefined rotor blade profile. For this purpose, the cable is glued into the cable conduit and the conduit is covered, sealed with filler paste and the filler paste is subsequently ground so that the contour matches the predefined outer contour of the profile of the rotor blade. This matching of the contour is of special importance since the rotor blade profile is an aerodynamically effective profile over essentially the entire span of the rotor blade and any deviation from a predefined target outer contour of the profile has a detrimental effect on the aerodynamic properties of the rotor blade. If the cable that has been installed in this manner fails, the filler paste has to be cut away and removed, while making sure that the load-bearing fiber-composite rotor blade structure is not damaged in this process. Consequently, repeated installation of a cable in and dismantling of a cable from a fiber-composite rotor blade is extremely complex and is associated with a great deal of production and assembly work as well as considerable costs. Therefore, it would be desirable if it were possible to could reduce the installation and dismantling work for the cable.